Allow clusters to be linked without a gateway #11226
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When a cluster has been installed without a gateway, it cannot be linked against, unless a load balancer service is used as an override. The service-mirror is tightly coupled with the notion of gateways. However, a gateway is not strictly necessary when clusters operate in a flat network. As part of this change, `linkerd multicluster link` has been changed to allow clusters without gateways to be linked against. When a cluster does not have a gateway, all services _must_ be exported in `remote-discovery` mode, otherwise routing wouldn't work. In addition, when a cluster does not have a gateway, linking against it will not create a probe service (since there is nothing to probe). Lastly, a check has been modified to ignore checking replicated endpoints when a service is in remote-discovery mode (to avoid false positives). Signed-off-by: Matei David <[email protected]>
Signed-off-by: Matei David <[email protected]>
alpeb
reviewed
Aug 10, 2023
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linkerd mc gateways is currently throwing an error currently for me, not sure if because I haven't totally set up things right locally. But most likely we'd like to filter out non-gateway remotes in there.
Also WDYT about having this flag be --gateway (defaults to true) instead to coincide with the linkerd mc install analog flag?
adleong
reviewed
Aug 10, 2023
Signed-off-by: Matei David <[email protected]>
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Tested this out end-to-end by branching out and merging the remote-disco changes: |
Signed-off-by: Matei David <[email protected]>
Signed-off-by: Matei David <[email protected]>
Signed-off-by: Matei David <[email protected]>
Signed-off-by: Matei David <[email protected]>
adleong
reviewed
Aug 11, 2023
multicluster/cmd/link.go
Outdated
| } | ||
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| if opts.gatewayAddresses != "" && !opts.enableGateway { | ||
| return nil, fmt.Errorf("--gateway-addresses and --gateway=false are mutually exclusive, received selector: %s", opts.selector) |
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Bad copy paste leaving the selector in the error message?
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Thanks, my bad. On second thought, I left it at "are mutually exclusive", it should be easy to spot any overrides passed in without having to log them.
Signed-off-by: Matei David <[email protected]>
adleong
approved these changes
Aug 15, 2023
alpeb
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Aug 16, 2023
This is a release candidate for stable-2.14.0; we encourage you to help trying it out! This edge release contains a number of improvements over the multi-cluster features introduced in the last edge release supporting flat networks. It also hardens the containers security stance by removing write access to the root filesystem. * Enhanced `linkerd multicluster link` to allow clusters to be linked without a gateway ([#11226]) * Added cluster store size gauge metric ([#11256]) * Disabled local traffic policy for remote discovery ([#11257]) * Fixed various innocuous multi-cluster warnings ([#11251], [#11246], [#11253]) * Set `readOnlyRootFilesystem: true` in all the containers, as they don't require write permissions ([#11221]; fixes [#11142]) (thanks @mikutas!)
alpeb
added a commit
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this pull request
Aug 16, 2023
This is a release candidate for stable-2.14.0; we encourage you to help trying it out! This edge release contains a number of improvements over the multi-cluster features introduced in the last edge release supporting flat networks. It also hardens the containers security stance by removing write access to the root filesystem. * Enhanced `linkerd multicluster link` to allow clusters to be linked without a gateway ([#11226]) * Added cluster store size gauge metric ([#11256]) * Disabled local traffic policy for remote discovery ([#11257]) * Fixed various innocuous multi-cluster warnings ([#11251], [#11246], [#11253]) * Set `readOnlyRootFilesystem: true` in all the containers, as they don't require write permissions ([#11221]; fixes [#11142]) (thanks @mikutas!)
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When a cluster has been installed without a gateway, it cannot be linked against, unless a load balancer service is used as an override. The service-mirror is tightly coupled with the notion of gateways. However, a gateway is not strictly necessary when clusters operate in a flat network.
As part of this change,
linkerd multicluster linkhas been changed to allow clusters without gateways to be linked against. When a cluster does not have a gateway, all services must be exported inremote-discoverymode, otherwise routing wouldn't work.In addition, when a cluster does not have a gateway, linking against it will not create a probe service (since there is nothing to probe). Lastly, a check has been modified to ignore checking replicated endpoints when a service is in remote-discovery mode (to avoid false positives).